Fishery Resources Monitoring System

Français
Norway lobster - North Sea (Fladen), 2008
Marine Resource  Fact Sheet
ICES Advice 2009
Norway lobster - North Sea (Fladen), 2008
Fact Sheet Citation  
Nephrops in Division IVa, West of 2oE, excluding Management Area F (Management Area G)
Owned byInternational Council for the Exploration of the Sea (ICES) – More
Related observationsLocate in inventorydisplay tree map
 
Species:
FAO Names: en - Norway lobster, fr - Langoustine, es - Cigala
Geographic extent of Norway lobster - North Sea (Fladen)
Main Descriptors
Considered a single stock: Yes        Spatial Scale: Sub-Regional
Management unit: Yes
 
 
Habitat and Biology
Depth zone: Shelf (50 m - 200 m).   Vertical distribution: Demersal/Benthic.  

Geographical Distribution
Jurisdictional distribution: National

Water Area Overview
Spatial Scale: Sub-Regional

Geo References
Resource Structure
Considered a single stock: Yes
Exploitation
 

Factors affecting the fisheries and the stock

In the Fladen area the Nephrops stock is restricted to a generally continuous area of muddy sediments extending from 57°30’N to 60°N, and from 1°W to 1°30’E, with other smaller patches to the north. The Fladen Ground is the largest known Nephrops ground where fishing activity can shift spatially so that effort can vary on parts of the ground.

Nearly three quarters of the landings are made by single-rig vessels and one-quarter by twin-rig vessels. 80 mm mesh is the commonest mesh size. Nearly 40% of the Nephrops landings at Fladen are reported as bycatch, in fisheries which may be described as mixed.

The effects of regulations

The minimum landing size for Nephrops on the Fladen Ground is 25 mm carapace length. Discarding takes place at sea, and rates averaged over the period 2005 to 2007 for this stock were 18% by number, or 11% by weight.

Changes in fishing technology and fishing patterns

In the early years of the fishery, effort was primarily directed to a region that could be reached within 12 hours steaming from ports along the NE coast of Scotland. In recent years, logbook information and GPS loggers show that vessels are fishing more widely over the ground, including to the far eastern and northern edges of the extensive mud area. High fuel prices may limit steaming to some of these areas in 2008.
Assessment
 
Assessment Model
Methodology

Scientific basis

Data and methods

The UWTV survey has been conducted since 1992. Potential bias in survey design has been detected and accounted for in the assessment this year (see “Data and methods” section at the start of section 6.4.14.)

Information from the fishing industry

The NSCFP stock survey shows an increase in Nephrops between 2001 and 2002, a slight decrease to 2003, and a marked increase up to 2007. Stock levels are considered to be similar or slightly less in 2008 (Figure 6.4.14.3). This information is broadly consistent with trends in the UWTV survey results.

Uncertainties in assessment and forecast

General comments are found at the start of section 6.4.14

The UWTV survey is conducted over the main part of the ground, representing an area of around 28 200 km2 of suitable mud substrate (the largest ground in Europe). The Fladen Ground Functional Unit contains several patches of mud to the north of the ground which are fished, bringing the overall area of substrate to 30 633 km2. This area is not surveyed but would add to the abundance estimate. The absolute abundance estimate for this ground is therefore likely to be underestimated by the current methodology.

Comparison with previous assessment and advice

The perception of stock in 2008 is similar to that in 2007 from the assessment in 2008.

The advice in 2008 was based on recent landings as the UWTV surveys were considered inappropriate to use as absolute indices of abundance. Following the outcome of the benchmark in 2009, the major concerns of the UWTV survey have been addressed and the survey is now considered a reliable estimate of absolute abundance.

The landings forecast for 2010 (equivalent to fishing at F0.1) is 16,419 tonnes. This is an increase of almost 4,000 tonnes on the reported landings in 2008.
Overall Assessment Results


Figure 6.4.14.3.1 Nephrops, Fladen (FU 7). Long-term trends in landings, effort, lpues, and mean sizes of Nephrops.


Figure 6.4.14.3.2 Nephrops, Fladen (FU 7). Time-series of the bias adjusted UWTV survey index estimates, with 95% confidence intervals.


Table 6.4.14.3.2 Nephrops, Fladen (FU 7). Total landings (tonnes).
Year All Nephrops gears combined Single rig Multirig
  Landings Effort LPUE Landings Effort LPUE Landings Effort LPUE
1981 304 8.6 35.3 304 8.6 35.3 na na na
1982 382 12.2 31.3 382 12.2 31.3 na na na
1983 548 15.4 35.6 548 15.4 35.6 na na na
1984 549 11.4 48.2 549 11.4 48.2 na na na
1985 1016 26.6 38.2 1016 26.6 38.2 na na na
1986 1398 37.8 37.0 1398 37.8 37.0 na na na
1987 1024 41.6 24.6 1024 41.6 24.6 na na na
1988 1306 41.7 31.3 1306 41.7 31.3 na na na
1989 1719 47.2 36.4 1719 47.2 36.4 na na na
1990 1703 43.4 39.2 1703 43.4 39.2 na na na
1991 3024 78.5 38.5 410 11.4 36.0 2614 67.1 39.0
1992 1794 38.8 46.2 340 9.4 36.2 1454 29.4 49.5
1993 2033 49.9 40.7 388 9.6 40.4 1645 40.3 40.8
1994 1817 48.8 37.2 301 8.4 35.8 1516 40.4 37.5
1995 3569 75.3 47.4 2457 52.3 47.0 1022 23.0 44.4
1996 2338 57.2 40.9 2089 51.4 40.6 249 5.8 42.9
1997 2713 76.5 35.5 2013 54.7 36.8 700 21.8 32.1
1998 2291 60.0 38.2 1594 39.6 40.3 697 20.5 34.0
1999 2860 76.8 37.2 1980 50.3 39.4 880 26.5 33.2
2000 2915 92.1 31.7 2002 62.9 31.8 913 29.2 31.3
2001 3539 108.2 32.7 2162 65.8 32.9 1377 42.4 32.5
2002 4513 109.6 41.2 2833 58.9 48.1 1680 50.7 33.1
2003 4175 53.7 77.7 3388 42.8 79.2 787 10.9 72.2
2004 7274 56.1 129.7 6177 47.5 130.2 1097 8.6 127.6
2005 8849 61.3 144.4 6834 43.4 157.5 2015 17.9 112.7
2006 9396 65.7 143.0 7149 50.2 142.4 2320 15.5 149.7
2007 11055 69.6 158.8 8232 52.2 157.7 2822 17.4 162.2
2008 11432 80.3 142.4 8247 58.8 140.3 3185 21.5 148.1


Table 6.4.14.3.3 Nephrops, Fladen (FU 7). Survey indices with and without bias adjustment. Values after 2002 have been adjusted for revised camera parameters
Year Mean
density
Abundance 95%
confidence
interval
Adjusted for bias 95%
confidence
interval
           
           
  burrows/m² millions millions millions millions
1992 0.17 4942 508 3661 376
1993 0.21 6007 768 4450 569
1994 0.30 8329 1099 6170 814
1995 0.24 6733 1209 4987 896
1996          
1997 0.13 3736 689 2767 510
1998 0.18 5181 968 3838 717
1999 0.20 5597 876 4146 649
2000 0.17 4898 663 3628 491
2001 0.23 6725 1310 4981 970
2002 0.29 8217 1022 6087 757
2003 0.27 7488 1452 5547 1076
2004 0.27 7729 1391 5725 1030
2005 0.21 5839 894 4325 662
2006 0.23 6564 836 4862 619
2007 0.34 9473 986 7017 730
2008 0.35 9857 1377 7302 1020

Reference Point
 


F

reference point

Harvest

ratio

Technical basis
F0.1 9.3% WKNEPH 2009
Fmax 15.8% WKNEPH 2009
(unchanged since 2009)


Scientific Advice

Single-stock exploitation boundaries

ICES advises on the basis of exploitation boundaries in relation to high long term yield and low risk of depletion of production potential that the Harvest Rate for Nephrops fisheries should not exceed F0.1. This corresponds to landings of no more than 16 419t for the Fladen Ground


Basis: Bias corrected survey index (2008) = 7302
Rationale Harvest rate

Landings 2010

(tonnes)

  5.0% 8827
F 2008 8.0% 14124
F0.1 9.3% 16419
  10.0% 17655
  15.0% 26482
Fmax 15.8% 27895
  20.0% 35310


Table 6.4.14.3.1 Nephrops, Fladen (FU 7). Single-stock exploitation boundaries (advice), management, and landings.
Year ICES advice

Recommended

Landings Fladen grounds (FU7)

ICES

Landings

FU71)

1989     2.3
1990     2.5
1991     4.2
1992   ~2.7 3.4
1993   2.7 3.5
1994   5.0 4.6
1995   5.0 6.4
1996   5.0 5.2
1997   5.0 6.2
1998   7.0 5.1
1999   7.0 6.5
2000   9.0 5.6
2001   9.0 5.5
2002   9.0 7.2
2003   9.0 6.3
2004   12.8 8.7
2005   <12.8 10.7
2006 No increase of effort - 10.8
2007 No increase in effort and harvest rate below 7.5% <10.9 11.9
2008 No new advice, same as for 2007 <10.9 12.24
2009 No increase in effort and recent average landings <11.3  
2010 Harvest Rate no greater than that equivalent to fishing at F0.1 <16.4  

Weights in ‘000 t.

1) Does not include discards.



Management
Management unit: Yes

Management Advice

Management considerations

To protect the stock in this Functional Unit, management is required to be implemented at the Functional Unit level.

Nephrops fisheries in this area have a bycatch of cod. In 2005, high abundance of 0 group cod was recorded in Scottish surveys near to this ground. This year class of cod has subsequently contributed to slightly improved cod stock biomass and efforts are being made to avoid the capture of cod so that the stock can build further. In 2008 over 90% of the Scottish industry was operating under a voluntary Conservation Credits scheme and has implemented real time closures with a view to reducing unwanted bycatch of cod.
Biological State and Trend
Exploitation rate: Undefined
Abundance level: Undefined

UWTV observations indicate that the stock is fluctuating without obvious trend with estimates for the last 2 years increasing to the highest abundance in the series. Considering the UWTV result alongside the indications of stable or slightly increasing mean sizes in the length compositions of catches (of individuals >35mm carapace length) suggests that the stock is being exploited sustainably. The decline in mean length of smaller individuals in the catch may be indicative of recent good recruitment.


Spawning biomass in relation to precautionary limits Fishing mortality in relation to precautionary limits Fishing mortality in relation to high long-term yield

Fishing mortality in relation to

agreed target

Comment

Unknown Unknown Unknown N/a  


Source of information
 
ICES.2009.Report of the ICES Advisory Committee, 2009. ICES Advice, 2009.
powered by FIGIS  © FAO, 2014
Powered by FIGIS
crawl